Hydrazese-containing fuel oil



Uited States Patent 9 HYDRAZINE-CONTAINING FUEL OIL COMPOSITION ArthurV. Churchill, Oakmont, and Edward Mitchell,

Valencia, Pa., assignors to Gulf Research Development Company,Pittsburgh, Pa., a corporation of Delaware No Drawing. Filed Dec. 2,1957, Ser. No. 699,911

4 Claims. (Cl. 44-64) This invention relates to improving the combustioncharacteristics of hydrocarbon oil fuels that normally tend to formsubstantial amounts of soot and smoke during combustion.

The petroleum industry has encountered a serious problem in satisfyingthe demand for middle distillate and heavier fuel oils that can beburned in oil burners such as those of the atomizing type and of therotary wallfiame type with little or no accompanying formation of smokeor soot. Oils that are normally burned in oil burners of the typesindicated are those of Number 2 grade or heavier, although lighter oilscan be used. Although some smoke and soot formation will normallyaccompany combustion of any suitable oil in burners of the typesindicated, especially where less than optimum combustion conditions areused, the problem is serious in the case of oils having an API gravityless than 34, as substantial smoking and soot formation will occurduring combustion of such oils, even when favorable combustionconditions are employed. The poor combustion characteristics of suchoils are considered attributable to the relatively high proportion ofaromatic components contained therein. Fuel oils having an API gravityof less than 34 will normally contain in excess of about 20 percentaromatics, for example, 25, 40 or even 60 percent or more of aromaticcomponents, whereas lighter fuel oils will normally contain asubstantially lower proportion of aromatics, for example, 15 percent orless. In the case of distillate oils, a high aromatics content usuallysignifies a large proportion of cracked distillates which are relativelyrich in aromatics. The proportion of catalytically cracked distillatefuel oils in commercially marketed fuel oils has increased in recentyears notwithstanding the relatively inferior burning qualities of suchoils, because the demand for fuel oils of comparable boiling range hasexceeded the available supply of straight-run oils.

Not only do low gravity distillate oils containing large proportions ofcracked distillates, that is, oils rich in aromatics, form greaterquantities of soot during combustion than straight-run, high-gravitydistillate oils, or similar oils low in aromatics, but also such oilsform soot of different quality. Soot formed from the latter oils is aloosely deposited, low-density material having a low coefiicient of heattransfer, whereas soot from the former oils is resinous, much denser andhas a higher coefiicient of heat transfer.

While the problem of clean combustion is especially serious in the caseof distillate fuels, where fuel quality is of major importance, acombustion problem also exists in the case of residual fuel oils.Similarly as the middle distillate fuel oils, the residual fuels have anAPI gravity less than 34 (API gravity for typical No. 6 varies in therange of to 15), and they also frequently contain exceptionally largeproportions, for example percent or more, of aromatic components.Residual fuels can contain relatively low-boiling aromatic components aswell as higher boiling materials, as they are frequently diluted orcut-back with lower boiling cracked distillate oils in order to reducethe viscosity of the heavier oils.

Although the combustion of fuel oils having an API gravity of less than34, and consequently a relatively large proportion of aromatics, willtend to produce soot and smoke in various atomizing burners ofconventional types, that is, burners in which the fuel oil is burned inthe form of a spray of liquid droplets in admixture with air, combustionof such oils in rotary wall-flame type burners constitutes an especiallysevere problem. In the latter instance the fuel oil is burned aftervaporization of the fuel oil by impingement thereof on a hot metalsurface.

Excessive smoking and soot formation during combustion of fuel oils isobjectionable not only from the standpoint of cleanliness and airpollution, but also in that smoke and soot lead to stack deposits whichmay reduce burner draft and/or cause the stack temperature to rise to adangerous point.

The present invention relates to improved fuel oil compositionscomprising hydrocarbon fuel oils that have an API gravity less than 34,which compositions have reduced smoke and soot forming tendencies duringcombustion, whereby such compositions are rendered more suitable for useas fuels in oil burners of various kinds, such as domestic heatingfurnaces of the atomizing or rotary wall-flame type, combustion gasturbine engines, and the like. We have found that such improved fuelcompositions can be obtained by incorporating in a fuel oil of the typedescribed and that normally tends to form smoke and soot in an atomizingtype burner, a small amount of hydrazine.

The exact mechanism by which hydrazine functions to reduce smoking andsooting during combustion of fuel oils of the class disclosed has notbeen definitely determined, and accordingly, We do not intend thepresent invention to be limited to any particular theory of operation.It may be that the hydrazine reduces the ignition temperature of theoil, thus enabling more complete combustion and at the same timereducing the possibility of thermal cracking of the oil prior tocombustion. On the other hand, it may be that the hydrazine causes theoil to burn at a higher temperature, thus facilitating more completecombustion. Regardless of the mechanism by which hydrazine functions inthe present invention available experimental evidence shows that adefinite reduction in smoke and soot forming tendencies is obtained bythe use of small amounts of this material in fuel oils that normallytend to promote excessive soot and smoke for mation during combustion inatomizing type burners.

The use of unsubstituted hydrazine is important for the purposes of thisinvention since unsubstituted hydrazine imparts distinctly superiorcombustion characteristics to fuel oils containing this material.

The hydrazine is added to the fuel oils in a proportion sufiicientsubstantially to reduce the smoking tendencies of the oil. The optimumproportion will vary to some extent according to the nature of the fueloil. The type of fuel oil burner employed can also affect the optimumproportion of agent to be added. Within the limits of theseconsiderations, we have found that best results are obtained by additionto the fuel oils of small amounts of hydrazine. Thus, a noticeableimprovement usually will be obtained by addition of as little as 0.02weight percent of this material to the fuel oil, and a major improvementwill be obtained by the addition of about 0.05 weight percent to thefuel oil. Normally, it will not be necessary to add the hydrazine inexcess of the latter proportion, but in some cases it may be desirableto employ the hydrazine in proportions up to its solubility limit in thefuel oil. 4

Hydrazine may be incorporated in the fuel oil in'any suitable manner.Thus, it can be added to the fuel oil either as such or in the form ofconcentrated solutions in mutual solvents for oil and polar substances,for example, butanol, ethylene glycol monobutyl ether, diethylene glycolmonobutyl ether, and the like. After addition of the hydrazine to theoil, some circulation of the oil is desirable to facilitate earlyformation of a homogeneous composition, but this is not absolutelyessential.

use in vaporizing pot-type burners) and having the followinginspections:

In order to demonstrate the extent of the improvement obtained with thetest additive, test fuel A was also subjected to the test withoutaddition of hydrazine.

In the following table there are tabulated the results obtained in thecombustion tests described above.

Table A Smoke Disc Number at- Compositlon Avg.

8% 8. 5% 9% 9. 5% 10% 11% 12% Smoke 00; C01 C02 CO: CO; C0; 00; Spot 1.Test Fuel A 1. 80 1.70 1. 75 1. 85 2.05 2. 50 3. 10 2.11 2. Test Fuel Aplus 0.05 Wt percent Hydrazine 1.40 1.00 0.85 0.80 0.90 1.35 2.00 1.19

In order to demonstrate the effectiveness of the combustion improvementagent disclosed'herein, hydrazine was incorporated in a No. 2 fuel oilthat normally tends to form smoke and soot on combustion, and thethuscompounded fuel oil was tested for smoking tendencies by combustionin an atomizing type burner. The test was carried out in a domestic oilburner (Timken, Model OFH-60Hi-Furnace). Conventional burner controlswere associated with the test apparatus in conjunction with electricaltimer relays to provide a minute on-lO minute ofi cycle of burneroperation. After permitting a warm-up of at least one 20 minute on phaseof burner operation with maximum combustion air, smoke spot and COreadings were taken at the middle of each on phase for 7 cycles usingdifferent air gate settings to regulate the quantity of combustion air.Changes of gate setting were made during burner off phases of the cycle.Smoke spot readings were obtained by withdrawing flue gas from asampling probe installed in the chimney pipe through a disc of No. 4Whatman filter paper one inch in diameter for 2 minutes. A vacuum pumpwas used to maintain a pressure differential of 2 1, inches Hg acrossthe disc. The smoke spot reading was then determined by means of aphotocell meter which had been calibrated using a Shell smoke spot chartgraduated in increasing shades of black ranging from zero (clean disc)to 9 (black disc) as the standard. The CO readings were obtained bywithdrawing flue gas through a sampling probe installed in the chimneypipe (according to United States Department of Commerce BulletinCS104-46) and by analyzing the flue gas for percent CG in an Orsattypeflue gas analyzer.

The test fuel, hereafter referred to as test fuel A, was acommercial-type, API gravity No. 2 fuel oil having an aromatics contentof about 45.5 percent and consisting of 34.1 volume percent straight runNo. 2 fuel oil distillate and 65.9 volume percent catalytically crackedNo. 2 fuel oil distillate, and that had been inhibited against sludgedeposition.

Percentages given herein are by weight of the composition unlessotherwise specified. The term No. 2 fuel oil is defined in ASTMStandards on Petroleum Products and Lubricants for November 1956 as adistillate oil for general purpose domestic heating for use in burnersnot requiring No. 1 fuel oil (an oil intended for The data presented inthe foregoing table indicate that a marked improvement in burningqualities of fuel oils 'is obtained by incorporation therein of thecombustion improvement agent of this invention. Thus, 0.05 percenthydrazine in test fuel A produced an average improvement of more than 43percent in the smoke spot number.

The test fuel described in the foregoing test is illustrative only.Substitution of other fuels disclosed herein in the foregoing testcompositions will produce similar benefits. Examples of other fuelcompositions included by this invention are shown in the followingtable.

It is emphasized that the problem with which the present invention isconcerned involves only fuel oils that are normally burned in fuel oilburners that utilize middle distillate and heavier oils and thatnormally exhibit severe smoking and soot forming tendencies in suchusage. As indicated, such oils are those having an API gravity less than34. The problem with which this invention is concerned is especiallyserious in the case of distillate fuel oils of the type described,because combustion quality is a primary consideration with such oils.Although a clean combustion problem also exists in the case of residualfuel oils suitable for use in atomizing type burners, the relatively lowprice of such fuels and the absence of a superior competitive fuelrenders the problem less serious in the case of such oils.

In order to demonstrate the nature of the problem with which the presentinvention is concerned, a number of fuel oils having varying densitiesand aromatics contents were subjected to a combustion test substantiallysimilar to that described above, but carried out in a Timken VerticalRotary Wall Flame Burner, Model F,

installed in a Weil-McLain Type 4-8-19 steam boiler, in order todetermine the burning characteristics of the oils. These tests werecarried out at 11.0% CO in the flue gas, a recommended figure for theburner model in question. The results of the tests are presented inTable C below:

Table C Gravity, Percent Smoke Fuel Oil API Argmat- Disc No.

1. FCC N0. 2 Distillate 25. 8 42 4. 4 2. 50/50 by Vol. Eastern VenezuelaSt.

Run and FCC No. 2 Dist 28.0 29. 3 2. 8 3. Fixed Bed Cat. racked No. 2Dist" 29.0 28. 7 3.0 4. TOO No. 2 Distillate 30. 9 24. 2. 2 5. 80/20 byVol. E.V.S.R. and FCC N0.

2 Dist 32.1 23. 2 l. 3 6. TOG Rafinate 34. 5 16.3 0.6 7. 50/50 TOORaffinate West Texas St. Run 35. 6 15.6 0. 6 8. Blend of Kerosene andGas Oil 41. 8 13. 9 0.4 9. Kerosene 42. 6 14.0 0.7

From the results shown in the foregoing table, it will be seen that fueloils having an API gravity of less than about 34 and an aromaticscontent of about 20 percent or more produce a relatively high smoke spotnumber which is a measure of the smoking and sooting tendencies of theoils. Even a small decrease in the API gravity of such lower gravityoils normally results in a disproportionate increase in the smoke spotrating. In contrast, oils having a gravity above 34 API produced a lowsmoke spot number and little difference in smoke spot number resulteddespite substantial differences in API gravity.

Aside from its value as a combustion improvement agent in oils of thetype described, hydrazine has especial value when employed incombustion-improving proportions in mixtures of straight-run andcatalytically cracked distillate fuel oils where the ratio ofcatalytically cracked to straight-run distillate is in the range ofabout 9:1 to 1:9 by volume. Such oils present an especially severeproblem with regard to sludge deposition during storage. It has beenfound that hydrazine not only improves the combustion characteristics ofsuch oils but also the stability thereof.

In order to demonstrate the effectiveness of hydrazine in the foregoingrespect, a blended distillate fuel oil of the type indicated andnormally tending to deposit sludge during storage, and containing asmall amount of hydrazine, was subjected to an accelerated stabilitytest. The accelerated test was carried out by storing a 4-ounce glassbottle of the oil in the dark for 24 hours at 210 F. At the conclusionof the test the oil sample was shaken and the quantity of sludgevisually rated according to the scale: none, trace, light, medium,heavy.

The test oil, hereinafter referred to as test oil B, was a No. 2 fueloil consisting of a mixture of 40 percent by volume doctor-sweetened,West Texas straight run No. 2 fuel oil distillate, 40 percent by volumeof light, fluid catalytically cracked gas oil boiling in the No. 2 fueloil range, and 20 percent by volume of a Thermofor catalytically crackedgas oil boiling in the No. 2 fuel oil range. The mixture had an APIgravity of 321 and an aromatics content of 37.8 percent.

In order to afford a basis for comparison a sample of test oil Bcontaining no hydrazine was also subjected to the same test.

The results of the foregoing stability test are set forth in Table D,following:

The foregoing data demonstrate the stabilizing effect of hydrazine onblended catalytically cracked and straight run distillate fuel oils.

If desired, the fuel oil compositions of this invention may contain inaddition to the compounds previously discussed, oxidation inhibitors,corrosion inhibitors, antifoam agents, ignition quality improvementagents, sludge inhibitors, color stabilizers and other addition agentsadapted to improve the oils in one or more respects.

Obviously, many modifications and variations of the invention as hereindescribed may be resorted to without departing from the spirit or scopethereof. Therefore, only such limitations should be imposed as areindicated in the appended claims.

We claim:

1. A fuel oil composition comprising a major amount of a hydrocarbonheating oil that has an API gravity less than about 34, and thatnormally tends to form smoke and soot during combustion in a heating oilburner, and containing a small amount, suificient to reduce the smokeand soot forming tendencies of the oil, of hydrazine, said small amountbeing a fraction of 1 percent by weight of the composition.

2. The fuel oil composition of claim 1 where said heating oil is a No. 2distillate fuel oil.

3. The fuel oil composition of claim 1 where said small amount is about0.02 to about 0.05 percent by weight of the composition.

4. A fuel oil composition comprising a major amount of a 9:1 to 1:9 byvolume mixture of straight run and catalytically cracked hydrocarbondistillate No. 2 heating oil that has an API gravity less than about 34,and that normally tends to form smoke and soot during combustion in a.heating oil burner, and containing a small amount, sufficient to reducethe smoke and soot forming tendencies of the oil, of hydrazine, saidsmall amount being a fraction of 1 percent by weight of the composition.

References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES Sci. Amen, vol. 189, No. 1, July 1953, Hydrazine, by Lessing,page 30.

The Chemistry of Hydrazine, by Andrieth et al., John Wiley and SonsInc., New York, 1951, p. 225.

1. A FUEL OIL COMPOSITION COMPRISING A MAJOR AMOUNT OF A HYDROCARBONHEATING OIL THAT HAS AN API GRAVITY LESS THAN ABOUT 34*, AND THATNORMALLY TENDS TO FORM SMOKE AND SOOT DURING COMBUSTION IN A HEATING OILBURNER, AND CONTAINING A SMALL AMOUNT, SUFFICIENT TO REDUCE THE SMOKEAND SOOT FORMING TENDENCIES OF THE OIL, OF HYDRAZINE, SAID SMALL AMOUNTBEING A FRACTION OF 1 PERCENT BY WEIGHT OF THE COMPOSITION.